Miranda's proposal, to be discussed at an upcoming council workshop, calls for building a treatment plant to purify effluent to drinkable quality, then inject it into the ground before it flows into the Hillsborough River, the city's primary source of drinking water.

Such a move would require state and federal permits. Miranda estimates the project would cost $200 million. The city hasn't conducted a cost analysis.

Miranda said utilities in Virginia, Texas and California return treated wastewater to drinking water supplies that well exceed state and federal water-quality standards.

In some cases, wastewater is filtered by reverse osmosis, which pressurizes the water and pushes it through a sheet of plastic. In others, it is exposed to ultraviolet radiation and mixed with hydrogen peroxide to destroy remaining micropollutants and organic matter.

Mayor Pam Iorio has cautioned against rushing the question to the ballot, saying that building a treatment plant likely would mean higher rates for the city's customers.

"As a city, we do not know what it would cost to implement a system that would turn reclaimed water into drinking water," she says in a recent memo. "Further, we would have to translate the costs to water rate increases that are currently unknown."

Beyond the stigma attached to drinking something that flowed through a sewer system, scientists recently have begun raising concerns about the potential for health risks.

Tampa's reclaimed water is treated enough for agricultural purposes but not for drinking.

In 2005, the U.S. Geological Survey conducted a study of treated wastewater from the city's Howard F. Curren Wastewater Treatment Plant and found 27 different micropollutants, though the water had undergone a filtration process.

The micropollutants included estrogens, steroids and anti-seizure and antibiotic medications.

The idea has been floated by the city before.

In the mid-1980s, Tampa spent more than $6 million on research for a similar proposal but backed away from it because of cost concerns and a lack of support from the public.

Reclaimed water from the city's wastewater treatment plant was fed to rodents in the 1990s to test for bacteria levels, toxicity, virus counts and chemicals. A panel of experts hired by the city to study health risks determined it was safe for consumption.

Tampa for years has struggled to expand its distribution system to put more reclaimed water on lawns and gardens to offset the city's potable water use. The reclaimed system serves only about 3,500 households in the South Tampa area, and plans to expand it to reach more residential customers were put on hold last year because of revenue shortfalls.

Both Tampa and Hillsborough County are under pressure from state environmental regulators to stop dumping unused treated wastewater into Florida's waterways. More than 55 million gallons of reclaimed water is dumped into Tampa Bay every day.

Even though the water is highly treated, it contains high levels of nitrogen that can rob natural water bodies of oxygen needed by fish, shellfish and other marine life.

Miranda says a drought that resulted in Tampa adopting the toughest watering restrictions in the state last year has proved that the city needs to save every drop.